Alarm device for detecting removal of or tampering with appliances or other articles

ABSTRACT

An electric alarm device for detecting removal or displacement of objects comprises a lamp of the thermostatic intermittent flashing type connected in series with a semi-conductor switch which is biased to its non-conducting position by a circuit including a wire conductor which when detached or broken removes the bias on the switch and causes the switch to conduct. A second switch arranged to be connected in series with an alarm actuating coil is biased to its off or non-conducting condition when there is no current flowing through the circuit of the first switch and is turned on or triggered when the lamp is energized and thereby produces intermittent energization of the alarm actuating coil and effects intermittent operation of the alarm. The device including the lamp is encapsulated in a rigid synthetic plastic block by a method which affords protection of the lamp from breakage due to pressure during curing of the plastic.

United States Patent 1 Hoecker 11] 3,742,480 June 26,1973

1 1 ALARM DEVICE FOR DETECTING REMOVAL OF OR TAMPERING WITII- APPLIANCESOR OTHER ARTICLES [75] Inventor: August C. Iloecker, Broomfield,

' Colo.

- [73] Assignee: Dean Nicholson, Pittsburgh, Pa.

[22] Filed:

NOV. 4, I971 [21] Appl. No.: 195,692

[56] References Cited UNITED STATES PATENTS 3,463,936 8/1969 Adem340/331 Almassy 340/331 Primary Examiner.lohn W. Caldwell AssistantExaminer-William M. Wannisky- Attorney-McGrew and Edwards 571 ABSTRACTAn electric alarm device for detecting removal or displacement ofobjects comprises a lamp of the thermostatic intermittent flashing typeconnected in series with a semi-conductor switch which is biased to itsnonconducting position by a circuit including a wire conductor whichwhen detached or broken removes the bias on the switch and causes theswitch to conduct A second switch arranged to be connected in serieswith an alarm actuating coil is biased to its off or nonconductingcondition when there is no current flowing through the circuit of thefirst switch and is turned on or triggered when the lamp is energizedand thereby produces intermittent energization of the alarm actuatingcoil and effects intermittent operation of the alarm. The deviceincluding the lamp is encapsulated in a rigid synthetic plastic block bya method which affords protection of the lamp from breakage due topressure during curing of the plastic.

6 Claims, 4 Drawing Figures pliances or other apparatus. These alarmshave for the most part been satisfactory for their intended uses,however, they have not proved fully adaptable for use in allapplications. It is, for example, desirable to provide a small, easilyconcealed alarm device for a wide range of applications. Accordingly, itis an object of the present invention to provide an alarm device ofimproved construction and operating characteristics for detecting thedisplacement of or tampering with selected objects.

It is another object of this. invention to provide a small and compactalarm device including an improved arrangement for facilitating its useinconcealed positions in automobiles and other locations,

It is another object of this invention to provide an im- -.proved methodfor making a compact encapsulated alarm device utilizing an electriclamp.

vBriefly, in carrying out the objects of this invention .in oneembodiment thereof, an alarm device is provided which includes a smallelectric lamp of the thermostaticintermittent type connected "in serieswith a transistor whichis biased to its nonconducting position by acircuit including a wire employed as a sensing element. A secondtransistor is employed as a switch arranged to be connected in serieswith a relay coil or other actuating device and, which is biasednormally to its off position; this second transistor is triggered by thepassage of current through the lamp circuit. Intermittent actuation ofthe alarm device results from intermittent energization of the lamp andconsequent intermittent removal of the bias on the second switch. Thelamp and circuit components'are encapsulated, and, in order to preventbreakage of the lamp, the glass bulb is first coated with a compressiblesilicone rubber and thereafter the entire device encapsulated in asuitable synthetic plastic potting compound.

The features of novelty which characterize this invention, together withfurther objects and advantages thereof, are pointed out withparticularity in the claims annexed to and forming a part of thisapplication, the invention itself, however, will best be understood byreference to the following description taken in connection with theaccompanying drawing in which;

FIG. I is a perspective view of an alarm unit embody- ,ing the inventionand indicating diagrammatically its connections for alarm purposes;

FIG. 2 is a perspective view of the mounting board and circuitcomponents of the unit of FIG. 1;

FIG. 3 is a sectional view through a broken away portion of the unit ofFIG. 1; and

FIG. 4 is a schematic diagram of the circuit connections of thecomponents illustrated in FIG. 2, illustrated as connected to actuate anautomobile horn.

Referring now to the drawing, the alarm actuating device illustrated inFIG. 1 comprises a body of rigid molded synthetic plastic material whichhas within it an embedded or encapsulated electronic circuit assemblyhaving ground terminals 11 and 12 extending laterally from the body l0.These terminals also constitute attaching lugs for securing the body 10in a selected position near the apparatus, device or object to beprotected by the alarm. Electric lead wires 13, 14 and 15 extend fromthe device 10 and are of sufficient length to facilitate the connectionof the device to the power supply and alarm actuator and to utilize thelead 13 for location through or around the object to be protected. Forpurposes of illustration, the diagrammatic circuit connection has beenindicated, and it is assumed that the device 10 is attachedto anautomobile in a suitably concealed position and that the lugs'll and 12are attached to the ground or common connection provided by the framemember of the automobile. The lead 13 is connected to the ground, asindicated by a bolt 16 connected to a frame member 17 of the automobilewhich constitutes the ground. The lead 13 has been indicated as passingthrough a device 18 which may, for example, be a stereo tape deckmounted in the automobile. The lead 14 is connected directly to thebattery of the automobile, indicated at 20, and the lead 15 is connectedto the battery through the coil of a relay 2] which is the horn relay ofthe automobile, normallyconnected across the battery 20 by pressing thehorn button.

The lead 13 is arranged so that if the device 18 is removedfrom itsnormal position the lead will be broken or broken loose from itsconnection to ground at 16. The opening of the circuit in this mannereffects actuation of the alarm device 10 and energizes the relay 2] toactuate the horn of the vehicle. For greatest reliability in detectingthe displacement or removal of an object such as the tape deck 18, thewire 13 is located so that there is minimum likelihood of detection ofits presence and the detecting device 10 is similarly located in aconcealed position. The alarm is sounded intermittently upon operationof the device of this invention and in a manner described in detailbelow.

The circuit assembly or chassis of the device 10, as illustrated in FIG.2, comprises an insulated mounting plate or base 22, on whichthe lugs 11and 12 are mounted, these .lugs being connected together by a suitableconductor such as a printed circuit connection. The components of thecircuit include an electric lamp 23 of the thermostatic intermittentflashing type, and as illustrated the lamp includes the usual attachingbase 25 and a glass bulb 24 and a stem 25 extending from the base andcarrying two conductors 26 and 27 and a bimetal strip 28. The filamentof the lamp, indicated at 30, is connected between the upper end of theconductor 26 and the upper end of the bimetal thermostat 28. At normaltemperatures, thebimetal strip 28 engages the upper end of the conductor27 when the filament 30 is not energized so that the filament 30 isconnected between the two conductors. The heat of the filament uponenergizationcauses the bimetal element 28 to made through printedcircuit conductors (not shown)- by soldered connections on the bottomside of the plate 22.

When the circuit assembly, illustrated in FIG. 2, has been completed, itis encapsulated in the block 10. This encapsulation is effected by firstcovering the lamp bulb 23 and also other possibly breakable components,such as the diode 33, with a compressible insulating material. Thiscovering may be accomplishedby enclosing the lamp and diode, forexample, with a compressible synthetic plastic material wrapped aboutthese components. Preferably the lamp bulb and any other componentswhich may be subject to damage upon compression are coated with acompressible silicone rubber, the coating being accomplished by brushingor dipping the parts in a liquid silicone material which is then allowedto cure. The entire assembly is positioned in a mold with the lugs 11and 12 and the leads 13, 14 and 15 protruding therefrom. The mold isthen filled with a suitable synthetic resin potting compound, such as apolyester resin or an epoxy resin, a

suitable catalyst or setting agent being added. After the compressiblelayer 38 prevents injury to the bulb regardless of the length of timerequired for full curing of the plastic body, and the encapsulated alarmdevices may be made in production with minimum likelihood of breakage. 1

The manner in which the circuit components illustrated in FIG. 2 areconnected to provide the alarm device of this invention is indicated inFIG. 4, wherein the components and circuit of the device are shown tothe left of a broken line 39 and the battery and horn circuit of anautomobile to the right. The lamp 23 is connected in series with thetransistor 31 between the high side of the battery or other source andground or the common negative line. The transistor 31 is biased to itsoff or nonconducting condition by the resistors 34 and 35, the base ofthe transistor being connected to the junction of these resistors. Thelead wire 13 which constitutes the alarm sensor is connected to theother end of the resistor 34 and when in use is connected to the groundas indicated to complete the bias circuit. The emitter of the transistor31 is connected through the resistance 36 to ground and the transistor32 is connected across the resistance 36, its base being connected tothe junction of the resistance 36 and the emitter lead of the transistor31 and the emitter of the transistor 32 being connected to ground. Whenno current is flowing through the transistor 31 and the lamp 23, thetransistor 32 is biased to its off or nonconducting position. The lead15 is connected to the collector of the transistor 32 and the diode 33is connected across the transistor 32 between-ground and the collector.Thus, when the lead 15 is connected in series with the coil of the relay21, indicated at 40, the relay will be actuated whenever the transistor32 is rendered conducting and upon opening of the transistor 32 byrestoration of its original bias, the reverse potential or inductivekick is dissipated through the diode 33. Energization of the coil 40closes the relay to connect a horn actuating coil 41 or other suitablealarm across the battery 20 to actuate the alarm.

When the device illustrated in FIG. 1 is connected as shown in FIG. 4,the transistor.3l remains in its nonconducting condition until such timeas the wire 13 may be broken or pulled from its ground or commonconnection. When this happens, the transistor 31 is rendered conductingand current flows through the lamp 23 heating the filament 30 andcausing current to flow through the resistance 36 to render thetransistor 32 conducting; this energizes the coil 40 and closes therelay switch 21 to energize the alarm coil 41. As soon as thetemperature of the bimetallic strip 28 in the lamp 23 reaches apredetermined value the strip moves away from the lamp conductor 27 andopens the filament circuit, thereby stopping the flow of current throughthe lamp and through the resistance 36, so that the negative bias of thetransistor 32 is restored and the coil 40 deenergized. Thereupon thereverse current is dissipated through the diode 33. As soon as the lampcools, the bimetal strip 28 moves back into contact with the conductor27 and the actuation of the alarm is repeated. The intermittentenergization of the alarm will continue until the lead 13 is againconnected to ground or until-the battery. is disconnected. The circuitthus operates to provide an intermittent alarm signal whenever the wire33 is broken or detached from ground.

For purposes of illustration, and not by way of limitation, an alarmdevice embodying the above-described invention was built and tested andfound fully effective for use'as an automobile accessory protectionalarm. The device as constructed included the circuit as illustrated inFIG. 4 to the left of the line 39, and the com ponents employed were thefollowing:

Resistance 34-33 ohms Resistance 35-] ,000 ohms Resistance 36-10 ohmsTransistor 31 was a 2N5225 transistorMotorola Transistor 32 was a 2N5294transistorSolitron Diode 33 was a lN4002Motorola The lamp was a GeneralElectric No. 257 thermo static flashing lamp The circuit as provided wasoperated on the l2-volt battery of an automobile The horn relay coil ofthe automobile was connected between the positive terminal of thebattery and through the lead 15 to the transistor 32. The device wasencapsulated using as the compressible covering 38 a silicone rubbersold by General Electric Company under the designation GE-RTVIOSSilicone Rubber.

It will be understood that, if desired, instead of employing NPNtransistors as the transistors 31 and 32, PNP transistors may beemployed; in this case the circuit is connected with the negativeterminal of the battery or other source connected to the lead 14 andground connected to the positive side of the battery. Also, theconnections of the diode 33 are reversed, whereupon the circuitemploying PNP transistors oper ates in the same manner as the circuit asillustrated in the drawing.

In the illustration of the circuit in FIG. 4, a conven tional automobilehorn button 42 has been illustrated which, upon closure, energizesthe-coil 40 by connecting it across the battery 20. No modification ofthis circuitry is required in order to utilize the coil 40 in the mannerillustrated for providing an alarm indication upon opening of thecircuit between the resistance 34 and the ground. For purposes ofillustration, the connection between the resistance 34 and ground hasbeen indicated as an extended length of wire 13 which is broken when theprotected apparatus or other item is removed; however, for differentapplications, other suitable connecting elements may be provided foropening the circuit between resistance 34 and ground upon tampering ordisplacement of the article to be protected by the alarm.

I claim: 1. As an article of manufacture, an alarm actuating devicecomprising, an electric lamp of the thermostatic intermittent flashingtype, means including a first switch for connecting said lamp across apower source, means for biasing'said first switch to its open condition,a second switch, means for connecting said second switch across saidpower source, means for biasing said second switch to its opencondition, and i means for utilizing current flowing through said lampand first switch for triggering said second switch to its closedcondition, whereby when said biasing means for said first switch isdisabledto render said first switch conducting said second switch willconduct and the current passing therethrough may be utilized to'actuatean alarm, the current through said second switch flowing intermittentlywith the intermittent operation of said lamp and the resultingintermittent biasing of said second switch. 2. An alarm actuating deviceas set forth in claim 1 wherein said means for biasing said first switchincludes an extended conductor constituting a sensor for engagement withan object, the displacement of which is to be detected.

3. An alarm actuating device as set forth in claim 1 wherein said firstand second switches are transistors, and including a diode connectedacross said second switch for by-passing current flowing in a reversedirection through said connecting means from said second switch. r

4. An alarm actuating device as set forth in claim 1, said lamp having acovering of compressible synthetic plastic material, and said devicebeing embedded in a block of rigid plastic material.

5. An alarm actuating device as set forth in claim 4, said coveringbeing a coating of a compressible silicone rubber.

means including a relay coil for connecting said second switch acrosssaid power source,

means for utilizing current flowing through said lamp and said firstswitch for triggering said second switch to its conducting conditionwhereby disabling of said biasing means for said first switch renderssaid first switch conducting and energizes said lamp to effectintermittent energization of said lamp and of said relay coil, and

means effective upon energization of said relay coil for actuating saidalarm.

1. As an article of Manufacture, an alarm actuating device comprising,an electric lamp of the thermostatic intermittent flashing type, meansincluding a first switch for connecting said lamp across a power source,means for biasing said first switch to its open condition, a secondswitch, means for connecting said second switch across said powersource, means for biasing said second switch to its open condition, andmeans for utilizing current flowing through said lamp and first switchfor triggering said second switch to its closed condition, whereby whensaid biasing means for said first switch is disabled to render saidfirst switch conducting said second switch will conduct and the currentpassing therethrough may be utilized to actuate an alarm, the currentthrough said second switch flowing intermittently with the intermittentoperation of said lamp and the resulting intermittent biasing of saidsecond switch.
 2. An alarm actuating device as set forth in claim 1wherein said means for biasing said first switch includes an extendedconductor constituting a sensor for engagement with an object, thedisplacement of which is to be detected.
 3. An alarm actuating device asset forth in claim 1 wherein said first and second switches aretransistors, and including a diode connected across said second switchfor by-passing current flowing in a reverse direction through saidconnecting means from said second switch.
 4. An alarm actuating deviceas set forth in claim 1, said lamp having a covering of compressiblesynthetic plastic material, and said device being embedded in a block ofrigid plastic material.
 5. An alarm actuating device as set forth inclaim 4, said covering being a coating of a compressible siliconerubber.
 6. An alarm system for detecting and indicating a displacementof an object comprising, an electric lamp of the thermostaticintermittent flashing type, means including a first semi-conductorswitch for connecting said lamp across a power source, means for biasingsaid first switch to its nonconducting condition, a secondsemi-conductor switch, means including a relay coil for connecting saidsecond switch across said power source, means for utilizing currentflowing through said lamp and said first switch for triggering saidsecond switch to its conducting condition whereby disabling of saidbiasing means for said first switch renders said first switch conductingand energizes said lamp to effect intermittent energization of said lampand of said relay coil, and means effective upon energization of saidrelay coil for actuating said alarm.